This invention relates to a method of laying a pipe underground and a system for carrying such method into practice.
In one method known in the art which is usually used for laying a pipe underground, the ground is excavated to form a groove in a position in which the pipe is to be laid, and one pipe after another is placed in the groove. This method is generally referred to as an open channel process in which it is necessary that a groove be dug deep below the surface of the ground when it is desired to lay a pipe deep underground, and this is not desirable because the operation is time-consuming. When the open channel process is used, difficulties are faced with particularly if the pipe is designed to be laid under the buildings. Methods known in the art to replace the open channel process includes a propulsion process in which a starting pit is dug and a pipe is made to penetrate the ground on the side of the pit by means of propelling cylinders while pipe segments are being connected together to form the pipe. The propulsion process has become a main process in laying pipes of a diameter below 800 mm. In the propulsion process, a multiplicity of pipe segments are connected together and driven through the earth by propulsion. Thus a high earth pressure would be applied to the lateral surface of the pipe assembly to offer high frictional resistance or adhesion resistance. Also, high resistance would be offered by the earth acting on the front surface of the head attached to the leading end of the pipe to the movement of the pipe through the ground. Thus a very high propelling force would be required to carry out pipe laying operation by the propulsion process, thereby entailing the use of a propulsion system of large size.